1. Field of the Invention
The present invention relates to a method of laser cutting metal interconnections in a semiconductor device. More specifically, it relates to an improvement in a method of laser cutting metal interconnections formed on a semiconductor wafer in a semiconductor device.
2. Description of the Prior Art
A well known method of cutting metal interconnections formed on a semiconductor wafer by laser beams is disclosed in "Laser Targeting Considerations in Redundunt Memory Repair" reported by D. Smart, R. Reilly, B. Wells et al. in Proc. Spie Int. Soc. Opt. Eng. (USA) Vol. 385, January 1983, pp. 97-101.
FIG. 1 is a conceptual schematic diagram showing a conventional laser trimming device. In FIG. 1, a laser beam 4 emitted from a laser beam source 1 is supplied through an optical system 2 to an optical beam positioner 3. The laser beam 4 emitted from the laser beam source 1 is supplied to the optical beam positioner 3 through the optical system 2 for the following reason: the energy of the laser beam directly emitted from the laser beam source 1 depends on the characteristics of crystals in the laser beam source 1 which is implemented by, e.g., a solid laser. Such energy is not constant and must be set as appropriate beam energy by the optical system 2. The optical beam positioner 3 is adapted to control positions of the laser beam 4 to be irradiated on metal interconnections, having a high melting point, which are formed on a semiconductor wafer 5. The high melting point metal interconnections formed on the semiconductor wafer 5 are cut by the irradiated laser beams 4.
In the conventional laser trimming apparatus, structured in the aforementioned manner, the high melting point metal interconnections are made molten and then are cut by the laser beams 4 in the atmosphere, whereby hot splashes of the molten metal interconnections are scattered and cause a short circuit between adjacent interconnections on the semiconductor device and damage in adjacent circuits.